Various ways are known to provide a transformer:
1. one begins by forming the electrical windings, then the magnetic circuit is formed around the electrical windings. This is the method which is generally used in Europe. Its main disadvantage is the discontinuity of the magnetic circuit (which is made either by coiling strips and cutting, or by the juxtaposition of parts cut from the strips), which represents a highly negative element for reaching an optimum economic efficiency. Moreover, the magnetic material is not fully used; PA0 2. or, a magnetic circuit is first made, then the electrical windings are coiled about the circuit thus obtained. The coiling operation can be carried out by using a toric coiling machine, but this technique is time-consuming and therefore costly, and is limited by the capacities of the presently available machines. The coiling can also be performed by rotating a cylindrical support about the magnetic circuit while winding the conductive wire or band on said support. This technique is of great interest but its development encounters the following practical difficulties, which are not yet overcome:
the coiling speed remains low, due to the small clearance between the winding support and the magnetic circuit, and due to the difficulty of positioning and stabilizing said two elements for this operation; PA1 the inputs and outputs of the electrical windings present problems, notably as regards their location, their passage through the windows of the magnetic circuits during coiling, and their protection during such operation; PA1 the adjustment, which is made after, of the electrical windings on the magnetic circuit remains difficult, and has to be done by the use of auxiliary mechanical systems which are complex and costly. The resistance to dynamic efforts, when short-circuits appear, of the electrical windings-magnetic circuit assembly, which is vital for the transformer, depends on this adjustment.
On the other hand, for practicing the two above methods, the materials are not used to their maximum capacity. Therefore, these known methods do not allow tending toward the smallest economic cost, as regards the manufacture and operation of the transformers thus made as well as the energy consumed ("Iron" losses due to the magnetic circuit and "Copper" losses due to the windings).